This invention relates generally to systems, apparatuses, and methods useful in testing the performance of a monolith catalyst. More specifically, this invention relates to systems, apparatuses, and methods for non-destructive testing of a monolith catalyst like those used in industrial engine emission control. Notwithstanding the above, the underlying principles could be used for testing any large monolith catalyst element.
There are two methods for testing the activity of a monolith catalyst. The first method removes a small portion of the catalyst element, places that portion or sample core into a small test system, and uses synthetic gas mixtures to test the core and determine the overall activity of the catalyst. For example, catalysts used in industrial engines have outside dimensions from about 6 to 40 inches across and the removed core can be about 1 inch diameter. The second method tests the entire catalyst element by installing the element into a system that passes either engine exhaust or a synthetic gas mixture over the element.
The first method, sampling, has two major disadvantages: sampling error and catalyst damage or failure. Sampling error comes about because the activity of the catalyst element can vary across its face. Therefore, the sample core may test at higher or lower activity than the element as a whole and introduce significant sampling error into the test results. Catalyst failure comes about in a couple of ways. First, because reinstalling the core into the element is challenging, the hole created by the removed sample core is often plugged to prevent flow passing through it. This reduces the available catalyst volume and detriments the performance of the catalyst element as a whole. Additionally, any leakage around the plug or reinstalled core impairs performance. Fear of damaging the element leads people to test a limited amount of it—and thereby increase sampling error—because every core removed presents another opportunity to damage the overall element. Second, the process of removing the core can cause loss of coating material in the core itself. This not only detriments the analysis but because some catalyst elements have layers of metal foil that are not bound together, the element can either fall apart or destroy its cellular structure. Roughly half of all industrial engine monolith catalyst manufacturers do not affix layers and cutting operations can shake off about half of the coating.
The second method, whole element testing, eliminates sampling error and catalyst failure, but it too has a couple of problems. First, the method is resource and cost intensive because an engine has to be used to generate the test gas or a synthetic gas mixture must be used. If a synthetic gas mixture is used, tanks must be purchased to supply the gas and the entire gas stream must be heated above 700° F. If an engine is used, it must be fueled and maintained. And the engine also introduces error to the testing because a wide range of factors affect engine exhaust, factors such as engine wear, ambient conditions, fuel quality, and oil quality. Second, the quality of data obtained from the test depends upon having the correct “space velocity,” that is, the correct ratio between the flow rate of gas through the catalyst and the volume of catalyst material. Because of the wide range of catalyst sizes and shapes employed by the various catalyst suppliers, the tester must have right equipment, jigs and fixtures to hold each size and shape in the gas flow. This leads to having a lot of equipment on-hand and the time consuming changeover that results. Additionally, the tester must produce sufficient gas flow for the specific catalyst either by using a series of engines or supplying a large amount of synthetic gas.
In summary, the first method, sampling, introduces significant sampling error and destroys a portion of the catalyst element. The second method, whole element testing, is very inefficient and difficult to set up given the wide range of sizes and shapes of catalyst elements employed by the industry.